Method and System for Facilitating a Persistent Memory-Centric System

1. A computer-implemented method, comprising: receiving a first request to write data to a non-volatile storage system, which comprises a first non-volatile memory associated with a latency which is less than a first predetermined threshold, a Not-AND (NAND) memory, and a second non-volatile memory associated with a latency which is greater than a second predetermined threshold; allocating a first physical address in the first non-volatile memory; writing the data to the first non-volatile memory based on the first non-volatile memory first physical address; mapping a logical page index associated with the data to the first non-volatile memory first physical address; and in response to determining that the data in the first non-volatile memory is not accessed within a first predetermined time period: copying the data from the first non-volatile memory to the NAND based on a physical page address in the NAND; and mapping the logical page index to the NAND physical page address.

2. The method of claim 1 , wherein the first non-volatile memory comprises a magnetoresistive random-access memory (MRAM) or a resistive random-access memory (ReRAM), and wherein the second non-volatile memory comprises a hard disk drive (HDD) or magnetic tapes.

3. The method of claim 2 , further comprising: in response to determining that the data in the NAND is not accessed within a second predetermined time period: copying the data from the NAND to the HDD based on a physical address in the HDD; and mapping the NAND physical page address to the HDD physical address.

4. The method of claim 2 , wherein in response to determining that the data in the MRAM is accessed within the first predetermined time period, the method further comprises: classifying the data based on an access frequency as hot data; and keeping the data in the MRAM; and wherein in response to determining that the data in the NAND is accessed within a second predetermined time period, the method further comprises: classifying the data based on an access frequency as hot data; and keeping the data in the NAND.

5. The method of claim 2 , wherein the storage system further comprises a Not-OR (NOR) memory, wherein the logical page index is mapped to the MRAM first physical address in a first entry of a first mapping table in the MRAM, wherein the logical page index is mapped to the NAND physical page address in a second entry of a second mapping table in the NOR, and wherein the NAND physical page address is mapped to the HDD physical address in a third entry of a third mapping table in the NAND.

6. The method of claim 5 , wherein in response to determining that the data in the MRAM is not accessed within the first predetermined time period, the method further comprises: classifying the data based on an access frequency as cold data; and invalidating the first entry of the first mapping table in the MRAM.

7. The method of claim 5 , further comprising: receiving a second request to write an update of the data previously written to the non-volatile storage system; allocating a second physical address in the MRAM; writing the updated data to the MRAM based on the MRAM second physical address; updating, in the first entry of the first mapping table in the MRAM, the mapping of the logical page index to the MRAM second physical address; invalidating the second entry of the second mapping table in the NOR; and marking as invalid the data stored at the NAND physical page address.

8. The method of claim 7 , further comprising: determining, based on the first mapping table, that the updated data of the second request corresponds to data previously written to the MRAM; and determining, based on the second mapping table, that the data previously written to the MRAM has been copied to the NAND, wherein the allocated second physical address in the MRAM is the same as the allocated first physical address in the MRAM, and wherein writing the updated data to the MRAM based on the MRAM second physical address causes an in-place overwrite at the MRAM first physical address.

9. The method of claim 5 , further comprising: identifying valid pages in the NAND; and evaluating the valid pages in the NAND based on a frequency of access by determining a classification for each respective valid page in the NAND.

10. The method of claim 9 , wherein in response to determining that the data in a respective valid page in the NAND is not accessed within a second predetermined time period, the method further comprises: classifying the data based on an access frequency as cold data; determining a new physical address in the HDD to which to copy the data; copying the cold data from the NAND to the HDD based on the HDD new physical address; mapping, in a fourth entry of the third mapping table, a respective physical page address of the respective valid NAND page to the HDD new physical address; invalidating, in the second mapping table in the NOR, an entry corresponding to the respective valid page in the NAND; and marking as invalid the data stored at the respective physical page address.

11. The method of claim 9 , further comprising: detecting a condition which triggers a garbage collection operation; identifying a first NAND block to be recycled; copying valid pages from the first NAND block to an available NAND block; and erasing the first NAND block.

12. The method of claim 2 , further comprising: loading an operating system (OS) image from the NOR; and launching a plurality of applications based on the non-volatile storage system, wherein the first physical address in the MRAM is allocated by a memory management unit associated with the non-volatile storage system, and wherein the memory management unit is configured to execute read/write requests by operating a cumulative physical space associated which the non-volatile storage system without requiring any logical storage drives or DRAM and without visibility into the NAND or the HDD, and wherein the cumulative physical space does not include any overprovisioned space associated with the MRAM, the NAND, or the HDD.

13. A computer system, comprising: a processor; and a memory coupled to the processor and storing instructions which, when executed by the processor, cause the processor to perform a method, the method comprising: receiving a first request to write data to a non-volatile storage system, which comprises a first non-volatile memory associated with a latency which is less than a first predetermined threshold, a Not-AND (NAND) memory, and second non-volatile memory which is associated with a latency which is greater than a second predetermined threshold; allocating a first physical address in the first non-volatile memory; writing the data to the first non-volatile memory based on the first non-volatile memory first physical address; mapping a logical page index associated with the data to the first non-volatile memory first physical address; and in response to determining that the data in the first non-volatile memory is not accessed within a first predetermined time period: copying the data from the first non-volatile memory to the NAND based on a physical page address in the NAND; and mapping the logical page index to the NAND physical page address.

14. The computer system of claim 13 , wherein the first non-volatile memory comprises a magnetoresistive random-access memory (MRAM) or a resistive random-access memory (ReRAM), and wherein the second non-volatile memory comprises a hard disk drive (HDD) or magnetic tapes.

15. The computer system of claim 14 , wherein the method further comprises: in response to determining that the data in the NAND is not accessed within a second predetermined time period: copying the data from the NAND to the HDD based on a physical address in the HDD; and mapping the NAND physical page address to the HDD physical address.

16. The computer system of claim 14 , wherein in response to determining that the data in the MRAM is accessed within the first predetermined time period, the method further comprises: classifying the data based on an access frequency as hot data; and keeping the data in the MRAM; and wherein in response to determining that the data in the NAND is accessed within a second predetermined time period, the method further comprises: classifying the data based on an access frequency as hot data; and keeping the data in the NAND.

17. The computer system of claim 14 , wherein the storage system further comprises a Not-OR (NOR) memory, wherein the logical page index is mapped to the MRAM first physical address in a first entry of a first mapping table in the MRAM, wherein the logical page index is mapped to the NAND physical page address in a second entry of a second mapping table in the NOR, and wherein the NAND physical page address is mapped to the HDD physical address in a third entry of a third mapping table in the NAND.

18. The computer system of claim 17 , wherein in response to determining that the data in the MRAM is not accessed within the first predetermined time period, the method further comprises: classifying the data based on an access frequency as cold data; and invalidating the first entry of the first mapping table in the MRAM.

19. The computer system of claim 17 , wherein the method further comprises: receiving a second request to write an update of the data previously written to the non-volatile storage system; allocating a second physical address in the MRAM; writing the updated data to the MRAM based on the MRAM second physical address; updating, in the first entry of the first mapping table in the MRAM, the mapping of the logical page index to the MRAM second physical address; invalidating the second entry of the second mapping table in the NOR; and marking as invalid the data stored at the NAND physical page address.

20. The computer system of claim 19 , wherein the method further comprises: determining, based on the first mapping table, that the updated data of the second request corresponds to data previously written to the MRAM; and determining, based on the second mapping table, that the data previously written to the MRAM has been copied to the NAND, wherein the allocated second physical address in the MRAM is the same as the allocated first physical address in the MRAM, and wherein writing the updated data to the MRAM based on the MRAM second physical address causes an in-place overwrite at the MRAM first physical address.

21. The computer system of claim 17 , wherein the method further comprises: identifying valid pages in the NAND; and evaluating the valid pages in the NAND based on a frequency of access by determining a classification for each respective valid page in the NAND.

22. The computer system of claim 21 , wherein in response to determining that the data in a respective valid page in the NAND is not accessed within the second predetermined time period, the method further comprises: classifying the data based on an access frequency as cold data; determining a new physical address in the HDD to which to copy the data; copying the cold data from the NAND to the HDD based on the HDD new physical address; mapping, in a fourth entry of the third mapping table, a respective physical page address of the respective valid NAND page to the HDD new physical address; invalidating, in the second mapping table in the NOR, an entry corresponding to the respective valid page in the NAND; and marking as invalid the data stored at the respective physical page address.

23. The computer system of claim 21 , wherein the method further comprises: detecting a condition which triggers a garbage collection operation; identifying a first NAND block to be recycled; copying valid pages from the first NAND block to an available NAND block; and erasing the first NAND block.

24. An apparatus, comprising: a non-volatile storage system, which comprises a magnetoresistive random-access memory (MRAM), a Not-AND (NAND) memory, and a hard disk drive (HDD); a memory management unit associated with the non-volatile storage system and configured to receive a first request to write data to the non-volatile storage system and allocate a first physical address in the MRAM; a table-managing unit configured to map a logical page index associated with the data to the MRAM first physical address; an MRAM-managing unit configured to write the data to the MRAM based on the MRAM first physical address; a NAND-managing unit configured to, in response to determining by the MRAM-managing unit that the data in the MRAM is not accessed within a first predetermined time period, copy the data from the MRAM to the NAND based on a physical page address in the NAND, wherein the table-managing unit is further configured to map the logical page index to the NAND physical page address; and an HDD-managing unit configured to, in response to determining by the NAND-managing unit that the data in the NAND is not accessed within a second predetermined time period, copy the data from the NAND to the HDD based on a physical address in the HDD, wherein the table-managing unit is further configured to map the NAND physical page address to the HDD physical address.